Surface Lignin Research Articles

Promoted lignocellulose fractionation and improved enzymatic hydrolysis of corn stalks through cationic surfactant combined with deep eutectic solvent pretreatment

The efficient conversion of lignocellulose relies on the implementation of an effective pretreatment strategy. Cationic surfactants combined with deep eutectic solvent ([Betaine][LA] was employed as a novel pretreatment strategy for treating corn stalks. Valuable insights were provided on the impact of the surfactant hydrophobic segment length on pretreatment efficacy. The specific pretreatment conditions were optimized by single factor and orthogonal experiment. Octadecyl trimethyl ammonium bromide (OTAB, 1.5 wt%) with the longest hydrophobic part combined with [Betaine][LA] (Betaine-to-LA molar ratio 1:4) achieved the best pretreatment effect (delignification 92.8 %, xylan elimination 91.1 %) when severity factor reached 4.26, meanwhile, 1.7 g/L xylo-oligosaccharides and 4.4 g/L furfural were detected in pretreatment liquid due to the hydrolysis of hemicellulose in corn stalks with acidic deep eutectic solvent [Betaine][LA]. The relative saccharification activity reached 2.7 times of raw material, while the lignin surface area significantly decreased, leading to enhanced cellulose accessibility. Additionally, molecular perspective provided by molecular dynamics showed the elimination of lignin and xylan was facilitated by strong interaction of hydrogen-bond and van der Waals force between lignin and hemicellulose with [Betaine][LA] + OTAB. Overall, the effectiveness and potential of cationic surfactant combined deep eutectic solvent pretreatment strategy for lignocellulose pretreatment was revealed.

Improving inter-fiber bonding by cellulase under a high surface lignin level

Lignin is behaving negatively in cellulase hydrolysis, leading to the high cost of cellulase in many areas. Instead of removing lignin, the fiber surface composition was changed in structure and distribution in this work through a light mechanical refining. 2 h of cellulase adsorption and hydrolysis were performed after that. The cellulase hydrolysis was found to be improved with the glucose production increasing from 0.031 to 0.074 g L−1. Hydrolyzed fibers were then made into handsheet for inter-fiber bonding properties characterization. With most lignin retained and more hydrogen bonding formed, both tensile index and zero-span tensile index were found to be improved after the cellulase modification. It can be concluded that the cellulase hydrolysis of fibers is positively correlated with the inter-fiber bonding properties.

Isolation of Highly Crystalline Cellulose via Combined Pretreatment/Fractionation and Extraction Procedures within a Biorefinery Concept.

Sustainable production of bio-based materials and chemicals requires integrated approaches which utilize all fractions of lignocellulosic biomass. In this work, highly crystalline cellulose was isolated via combined pretreatment/fractionation and extraction processes from beechwood sawdust. The proposed approach was based on the selective recovery of hemicellulose components in the first step, followed by enhanced delignification in the second step, permitting the efficient recovery of the remaining cellulose via bleaching in the final step. Hydrothermal pretreatment under tailored conditions in neat water or dilute acid resulted in almost complete hemicellulose removal (80-96 wt %) in the liquid fraction. In the second step, the formed surface lignin was isolated via mild extraction while enhanced removal of both native/structural and surface lignin (71 wt %) was achieved by applying the organosolv treatment using dilute sulfuric acid as catalyst. Dilute sulfuric acid pretreatment followed by acid catalyzed organosolv pretreatment proved to be the most efficient combined approach, leading to 80 wt % hemicellulose removal as xylose monomer, and 71 wt % delignification. High crystallinity cellulose (<88%), with an overall cellulose recovery of 68-91 wt % based on native cellulose in parent biomass was isolated in the last step via bleaching of all pretreated biomass solids. The proposed integrated biorefinery procedures that aim to whole "waste" biomass valorization, replacing fossil resources, with the use of green solvents (water, ethanol) at relatively mild temperature/pressure conditions, are in line with the scope of several United Nations Sustainable Development Goals, such as UN SDG 8, 11, 12, and 13.

Layer-by-layer assembling redox wood electrodes for efficient energy storage

The exploration of redox-active organic materials and low tortuous thick-electrodes is attractive for energy storage. The in-situ valorized lignin on raw wood surface accompanied by layer-by-layer deposition of electro-active materials endow such spatially distributed wood electrodes with high specific capacitance. Here, we report a layer-by-layer assembled ca.1.5 mm-thick redox wood hybrid electrode with 20 mg cm-2 electro-active mass loading for efficient energy storage. The in-situ modified surface lignin in treated wood (TrW) holds promise as redox-active material with enriched nanoporosity, carbonyl functionalities, and multi-phase ionic transport structure. The carbon nanotubes (CNTs) networking with in-situ polymerized polypyrrole (PPy) nanorods three-dimensionally in the lumen of TrW afford a wool-like, highly porous nanostructure. Such a hierarchical structured PPy@CNTs@TrW electrode offers a high areal capacitance of 1.46 F cm-2 with an extraordinary energy density of 0.983 mWh cm-3 (3.68 Wh kg-1) and power density of 5.4 mW cm-3 (20.25 W kg-1). Here, the valorized surface lignin contributes contributes to electrochemical energy storage accompanied by spatially distributed PPy@CNTs in low tortuous electrodes. The electrode offers extremely low electrochemical impedance of 0.61 Ω electrode resistance and 1.57 Ω electrolyte resistance. The hybrid wood electrode showcases even higher conductivity and energy/power density than thin carbonized wood and other state-of-the-art thin electrodes made of highly conductive three-dimensional networks. This work highlights the potential of in-situ valorized lignin in developing high-performance eco-friendly thick-electrodes for electrochemical energy storage applications.

Analysis of Aroma Components of Enzymatic Hydrolysis Products of Oak Lignin from Different Producing Areas

The morphology and structure of lignin in French oak, American oak and Chinese Mongolian oak were observed and compared by scanning electron microscopy (SEM). The results showed that the surface of lignin after enzymatic hydrolysis was more irregular and the contact area was obviously increased. GC-MS detected 3 kinds of lignin, 4 kinds of components and 30 kinds of volatile substances. The lignin content of French oak was the highest (8911.5 ± 512.2 μg/L, 29 kinds), followed by that of American oak (8071.7 ±541.9 μg/L, 26 kinds), and that of Mongolian oak was the least (7903.3 ± 492.5 μg/L, 26 kinds). The results of aroma characteristics analysis, principal component analysis and heat map analysis showed that the aroma components of the three kinds of oak lignin were significantly different. French oak lignin could provide more volatile phenols, with obvious smoky, woody and sweet flavor. Mongolian oak lignin carries more phenolic and ester compounds, providing a relatively soft floral, fruity flavor. American oak lignin has a relatively average aroma substance content, which can bring strong and complex complex aroma characteristics.

Lignin nanoparticles as a highly efficient adsorbent for the removal of methylene blue from aqueous media

This work demonstrated enhanced adsorption capabilities of lignin nanoparticles (LNPs) synthesized via a straightforward hydrotropic method compared to pristine lignin (PL) powder for removing methylene blue dye from aqueous solutions. Kraft lignin was used as a precursor and p-toluenesulfonic acid as the hydrotrope to produce spherical LNPs with ~ 200 nm diameter. Extensive characterization by SEM, AFM, DLS, zeta potential, and BET verified successful fabrication of microporous LNPs with fourfold higher specific surface area (14.9 m2/g) compared to PL (3.4 m2/g). Significantly reduced particle agglomeration and rearranged surface chemistry (zeta potential of −13.3 mV) arising from the self-assembly of lignin fractions under hydrotropic conditions enabled the application of LNPs and superior adsorbents compared to PL. Batch adsorption experiments exhibited up to 14 times higher methylene blue removal capacity, from 20.74 for PL to 127.91 mg/g for LNPs, and ultrafast equilibrium uptake within 3 min for LNPs compared to 10 min for PL. Kinetic modeling based on pseudo-first-order and pseudo-second-order equations revealed chemisorption as the predominant mechanism, with a rate constant of 0.032825 g/mg·h for LNPs—over an order of magnitude higher than PL (0.07125 g/mg·h). Isotherm modeling indicated Langmuir monolayer adsorption behavior on relatively uniform lignin surface functional groups. The substantially augmented adsorption performance of LNPs arose from the increased surface area and abundance of surface functional groups, providing greater accessibility of chemically active binding sites for rapid dye uptake. Overall, this work demonstrates that tailoring lignin nanoparticle structure and surface chemistry via scalable hydrotropic synthesis is a simple and sustainable approach for producing highly efficient lignin-based nano-adsorbents for organic dye removal from industrial wastewater.

Full utilization of poplar sawdust with chemical-mechanical pretreatment for coproduction of xylooligosaccharides, fermentable sugars and porous carbon materials

In recent decades, one of the major challenges of biorefinery is the full utilization of lignocellulosic components for coproduction of value-added materials. In this context, we proposed an integrated process of acetic acid (AC) pretreatment, Papir Forsknings Institutet (PFI) refining and enzymatic hydrolysis to coproduce xylooligosaccharides, fermentable sugars and lignin-based porous carbon materials. Results showed AC pretreatment (170 ºC, 60 min, 5 w/v % acetic acid and 5% 2-naphthol addition based on dry mass of biomass) resulted in maximum xylooligosaccharids (XOS) yield of 51.08%. The integrated process of AC pretreatment assisted by 2-naphthol-7-sulfonate addition and PFI post-refining led to cellulose hydrolysis yield of 98.20% and lignin-based porous carbon materials with methylene blue adsorption capacity of up to 749.17 mg/g. Moreover, it was found lignin repolymerization inhibitors (i.e. 2-naphthol, 2-naphthol-7-sulfonate) in acid pretreatment helped increase the specific surface area of substrate and decrease surface lignin coverage, which enhanced cellulose accessibility to cellulase enzymes. Moreover, they enhanced lignin detaching during enzymatic hydrolysis, which reduced cellulase aggregation and promoted the ease of cellulose hydrolysis. Results demonstrated an efficient pretreatment strategy to maximize coproduction of xylooligosaccharids, fermentable sugars and lignin materials from lignocellulosic biomass for full utilization.

High-performance and economic biodegradable composites based on polybutylene adipate terephthalate and modified lignin

Polybutylene adipate terephthalate (PBAT) is a biodegradable polymer with promising properties, but its wide-spread application is limited by factors such as high cost, suboptimal mechanical characteristics, and slow biodegradation rate. In this study, these limitations are addressed by incorporating low-cost lignin, modified with an isocyanate compound, into PBAT via an extrusion process. By investigating the effects of varying isocyanate content on the lignin surface, the optimal modification conditions at room temperature are identified over 48 h. Additionally, the maximum lignin content (5 wt%) is determined within the composite to achieve a balance between mechanical, thermal, and biodegradation properties while also considering the economic and environmental feasibility of the polymer composite. The research delved into the examination of both the minimum selling price (MSP) and global warming potential (GWP) for all PBAT-mLigA composites. The optimized PBAT-mLigA composites exhibited a notable reduction of up to 7% in both MSP and GWP when compared to pure PBAT. The predominant determinants influencing the economic and environmental potentials of these composites are the pricing of PBAT and the ratio in which it is incorporated into the proposed composites.

Construction of novel phytic acid-based lignin for highly efficient treatment of low-level radioactive wastewater: Synthesis, performance, and mechanistic insights

Low-level radioactive wastewater exhibits a serious jeopardize to the ecology, natural environment, and human health. Hence, this study constructed a novel adsorbent (PA-EHL) via a simple grafting reaction by using enzymatic hydrolysis lignin waste (EHL) and phytic acid (PA) as raw materials. The adsorption capacity of PA-EHL was evaluated using Ce(III) and La(III) as the representative nuclides. PA grafting significantly promoted the formation of good textural properties, high crystalline stability, and abundant phosphorous/oxygen-containing functional groups on lignin surface, thus appreciably strengthening the adsorption performance. The PA-EHL exhibited high adsorption capacity for Ce(III) with 743.16 and for La(III) with 735.60 mg/g within 240 min. In addition, the efficient ability of PA-EHL for adsorbing Ce(III) and La(III) displayed superior anti-ions interference abilities, excellent reusability, and extremely low operational fees. The P-O on PA-EHL surface as the main active site, displayed strong binding affinity for Ce(III) and La(III) via electrostatic attraction-dominated physisorption and complexation-dominated chemisorption, respectively. In summary, the constructed PA-EHL addresses the drawback of conventional adsorbents in view of complicated fabrication process, low adsorption capacity, inferior anti-ions interference abilities, and expensive cost, which makes it as a potential adsorbent in industrial application for the highly efficient treatment of low-level radioactive wastewater.

An integrated pretreatment strategy for enhancing enzymatic hydrolysis efficiency of poplar: Hydrothermal treatment followed by a twin-screw extrusion

To reduce the dependence on chemical inputs during biomass pretreatment, an integrated process on the basis of hydrothermal pretreatment followed by twin-screw extrusion for poplar was proposed. A comparative study was conducted on the pore structure, crystallinity, relative surface lignin concentration, cellulose accessibility, and enzymatic hydrolysis efficiency of the pretreated materials. Results suggested that the relative surface lignin concentration of fibers pretreated by hydrothermal treatment (conducted at 170 ℃ for 90 min) coupled with extrusion (HE) treatment was decreased compared to the sole hydrothermal (H) process, which had a positive impact on the subsequent enzymatic hydrolysis. Additionally, the HE process resulted in an increase in pore size by 34.4%, pore volume by 447.5%, and specific surface area by 93.5%, which enhanced the penetration and interaction of water into the fibers and thus increased cellulose accessibility by 143.2%. SEM and TEM observations revealed that fibers were separated and finely fibrillated, large amounts of fragmentary structure and cracks appeared on the fiber. In addition, the cell wall structure was deformed and damaged, when pretreated by HE process. Overall, this work showed that hydrothermal treatment followed by twin-screw extrusion was an achievable strategy for high fermentable sugar production of hardwood.

Sulfomethylation reactivity enhanced the Fenton oxidation pretreatment of bamboo residues for enzymatic digestibility and ethanol production.

Bamboo is considered a renewable energy bioresource for solving the energy crisis and climate change. Dendrocalamus branddisii (DB) was first subjected to sulfomethylation reaction at 95°C for 3h, followed by Fenton oxidation pretreatment at 22°C for 24h. The synergistic effect of combined pretreatment dramatically improved enzymatic digestibility efficiency, with maximum yield of glucose and ethanol content of 71.11% and 16.47g/L, respectively, increased by 4.7 and 6.11 time comparing with the single Fenton oxidation pretreatment. It was found that the hydrophobicity of substrate, content of surface lignin, degree of polymerization, and specific surface area have significant effects on the increase of enzymatic saccharification efficiency. It also revealed that sulfomethylation pre-extraction can improve the hydrophilicity of lignin, leading to the lignin dissolution, which was beneficial for subsequent Fenton pretreatment of bamboo biomass. This work provides some reference for Fenton oxidation pretreatment of bamboo biomass, which can not only promote the utilization of bamboo in southwest China, but also enhances the Fenton reaction in the bamboo biorefinery.

Kinetic understanding of fiber surface lignin effects on cellulase adsorption and hydrolysis

Cellulase hydrolysis is strongly affected by adsorption, which is inhibited by the non-productive binding between cellulase and lignin. However, lignin-bonded cellulase has also been found to be active in hydrolysis. Thus, in this work, lignin effects on cellulase adsorption and hydrolysis were studied using fibers with various surface lignin contents and structures based on kinetics. The surface lignin was changed by mechanical refining. Cellulase adsorbed on lignin showed reactivity to hydrolyze cellulose nearby according to the kinetic results, which is, however, much weaker compared with that by cellulose-bonded cellulase. With the decrease of surface lignin, this reactivity is also decreasing. Both cellulase adsorption and hydrolysis were increasing at first and then decreasing with the decrease of surface lignin as well as the lignin re-adsorption. It was concluded that lignin plays an important role in cellulase adsorption and non-productive binding occurs more easily between cellulase and the re-adsorbed lignin, as well as the residual lignin. At a relatively high surface lignin level, lignin structural and distribution changes were found to have a better effect on cellulase hydrolysis compared with lignin removal.

Enhancing enzymatic digestibility of bamboo residues using a combined low severity steam explosion and green liquor-sulfite pretreatment.

In this study, the effect of the green liquor (GL)-sulfite pretreatment on bamboo for enzymatic hydrolysis was investigated. The performance characterization of the pretreated bamboo substrates, including the chemical composition, and the structural characteristics was carried out. The results showed that 91.3% of lignin removal was achieved when the sample was treated with a GL loading of 12.0 mL per g-DS at 120 °C for 1 h. After 120 h hydrolysis with 18 FPU per g-cellulose for cellulase and 27 CBU per g-cellulose for glucosidase, the glucose yield increased from 54.6% to 89.6%. The SE-treated bamboo could bind more easily to cellulase than GL-sulfite treated bamboo could. The structural changes on the surface of the samples were characterized by SEM. The results indicated that the surface lignin could be effectively removed during pretreatment, thereby decreasing the enzyme-lignin binding activity.

Wood waste-derived dual-mode materials paving the way for year-round energy saving in buildings.

In the face of the challenges posed by global warming, traditional methods of building heating and cooling contribute significantly to electricity and coal consumption, thereby emitting considerable amounts of greenhouse gases. Here, a dual-mode thermal management structural material is created by processing sustainable cellulose and lignin derived from wood waste into gels, followed by lamination. The cellulose surface of the material exhibits the ability to scatter solar radiation backward while emitting strongly in the mid-infrared wavelengths, whereas the lignin surface absorbs visible and near-infrared light, primarily releasing energy through non-radiative transitions. Consequently, the material can achieve sub-ambient radiative cooling of 6 °C and solar heating of 27.5 °C during the daytime by simply flipping its orientation. This pioneering material showcases the potential to significantly reduce cooling energy consumption by an average of 18% and heating energy consumption by 42%. Moreover, the integration of a thermal-electric generator within the dual-layer structure optimally utilizes the temperature differential between the two layers, converting it into electrical power. Notably, the dual-mode thermal management structural material exhibits impressive mechanical strength, boasting a flexural strength of 102 MPa, surpassing that of natural wood by over 4.8 times. With its dual-mode functionality and embedded thermal-electric generator, this material represents a crucial step towards achieving both thermal comfort and energy autonomy in sustainable building practices, thereby contributing to a more environmentally friendly and efficient future.

Alleviating lignin repolymerization facilitated the combined acid and deep eutectic solvent pretreatment of Populus

To elucidate the effects of lignin repolymerization on the combined pretreatment, the sequential acid and deep eutectic solvent (DES) pretreatment was implemented on Populus (poplar) in this study. Effects of acid pretreatment with or without phenolic additives (2-naphthol (2 N) and resorcinol (RS)) on the DES post-treatment efficiency were examined. The results showed that 2 N inhibited the lignin repolymerization in the first-step pretreatment, and slightly enhanced the lignin removal during DES post-treatment. However, RS intensified the lignin repolymerization, significantly decreasing the delignification of DES post-treatment from 73.6%∼79.4% to 39.0∼43.0%. Moreover, the poorer enzymatic hydrolysis was observed in the combined pretreated substrates as compared to the single DES pretreated ones, due to the higher surface lignin coverage. The addition of 2 N counteracted the adverse effects of acid pretreatment on the hydrolysis yields of combined pretreated substrates, and facilitated the yields from 25.8%∼36.0% to 26.2∼67.3%, while the RS addition further decreased the hydrolysis yields to 8.6∼9.6%. The mechanism for the changes on enzymatic digestibilities of the combined pretreated substrates was elucidated.

Mechanism analysis of Lignin's effect on Asphalt's resistance to moisture damage

The present study investigates the mechanism by which lignin enhances the moisture resistance of asphalt materials, employing a combination of atomic force microscopy (AFM) and molecular simulations. The research aims to understand the changes in surface morphology and adhesion properties of asphalt upon immersion, and elucidate the role of lignin modification in mitigating the reduction of adhesive forces. AFM measurements reveal that lignin-modified asphalt exhibits higher adhesion force after moisture damage, possibly attributable to less nanostructures on the surface of lignin modified asphalt. Molecular dynamics simulations are employed to study the binding energies between lignin and different asphalt constituents. The results demonstrate that lignin exhibits the strongest binding affinity with asphaltene molecules, and also displays significant binding affinity with a specific saturated molecule. Furthermore, diffusion of water molecules on asphalt surfaces is investigated, revealing that lignin-modified asphalt exhibits lower water molecule diffusion coefficients and reduced binding energies. Finally, a spherical water molecule model is employed to analyze the wetting behavior on lignin-modified asphalt surfaces, illustrating the dual mechanism of lignin molecules resisting water molecules and inhibiting the binding of polar molecules within asphalt to water molecules. The findings of this research provide insights into the enhancement of moisture resistance in asphalt materials through lignin modification. The combination of AFM and molecular simulations offers a comprehensive understanding of the morphological and adhesive changes at the nanoscale, as well as the fundamental molecular interactions involved. The results contribute to the development of strategies for designing and engineering asphalt materials with improved resistance to moisture damage.

Integrated understanding of acidic deep eutectic solvent choline chloride: Oxalic acid pretreatment to enhance the enzymatic hydrolysis of rape straw

Using choline chloride (ChCl) as hydrogen-bonded-acceptor (HBA) and oxalic acid (OA) as hydrogen-bonded-donor (HBD), deep eutectic solvents (DESs) with different HBD-to-HBA molar ratios were synthesized to pretreat rape straw (RS). The influence of DES treatment on the RS chemical composition, structure change, and enzymatic saccharification were explored. DESs with low molar ratio of HBD-to-HBA exhibited low viscosity, which enhanced the pretreatment efficiency. When HBA-to-HBD molar ratio was 1:3, the delignification and enzymatic digestion efficiency were only 60.6% and 41.8%. As the molar ratio of OA decreased, delignification and enzymatic digestion efficiency increased to 83.6% and 96% (ChCl:OA = 3:1, mol/mol). After pretreatment (severity factor LogR0 =2.66), the cellulose accessibility and crystallinity increased from 353.0 to 691.1 mg/g and 35.4–64.2%, respectively. The lignin surface area decreased from 596.3 to 201.9 m2/g. The significant increase in cellulose accessibility and the decrease in lignin surface area explained the efficient enzymatic hydrolysis efficiency.

Facilitating enzymatic hydrolysis efficiency of rape straw by pretreatment with a novel glycerol-based deep eutectic solvent

Deep eutectic solvent (DES) pretreatment plays an indispensable role in destroying the natural anti-degradation barrier structure of lignocellulose. Here, the cetyltrimethylammonium bromide and glycerol were used to synthesize novel DES and introduced to the pretreatment process to facilitate the enzymatic hydrolysis efficiency of rape straw (RS). The results showed that the delignification and xylan removal could extremely reach 46.1% and 52.7% under optimal conditions (molar ratio of 1:6, 200 °C, 90 min), respectively. It also resulted in 171.4 mg/g higher accessibility, 7.2% higher crystallinity, and 122.3 m2/g lower lignin surface area in RS concerning morphological changes of deconstructed and porous cell wall structure. Ultimately, the reducing sugar yield of RS was increased from 27.4% to 67.9% after pretreatment with this type of DES. This study exploited a novel DES for facilely reducing the recalcitrance of lignocellulose and a promising process for efficient saccharification using renewable biomass.

Integrated understanding of enhancing enzymatic hydrolysis of bulrush through the metal chloride-assisting choline chloride: Glycerol pretreatment

To improve the saccharification efficiency of bulrush, the supplementary of metal chlorides in pretreatment of lignocellulose had been researched. The effect of metal chloride type and dosage on the ability of deep eutectic solvent (DES ChCl: Gly) pretreatment was evaluated by composition analysis of biomass, characterization analysis [scanning electron microscope, Fourier transform infra spectra, X-ray diffraction, accessibility of cellulose (Direct red dye adsorption experiment), surface area of lignin (Azure B dye adsorption experiment)], and enzymatic saccharification. One-pot pretreatment of bulrush using the AlCl3/ChCl:Gly (molar ratio, 1:2:0.06) with the solid liquid ratio of 1:10 (w:w), lignin (70.8%) and hemicellulose (87.7%) could be effectively removed, and the enzymatic saccharification yield could reach 90.1%, much higher than that of raw bulrush (21.4%). AlCl3/ChCl:Gly pretreated bulrush showed an apparent reduction in lignin surface area due to lignin removal. The correlations between the Azure B dye adsorption data and delignification [Y(delignification) = 0.29 × X(surface area of lignin) + 226.9, R2 = 0.90] and glucose yield [Y(glucose yield) = −0.31 × X(surface area of lignin) + 247.9, R2 = 0.93] were observed during the AlCl3/ChCl:Gly pretreatment. This constructed pretreatment system could improve the bioconversion efficiency of bulrush, which had potential application in biorefinery of lignocellulose.

Bio-based composites made from bamboo fibers with high lignin contents: a multiscale analysis

ABSTRACT To meet societal and economic expectations, the bio-based composite market is developing. However, some issues remain, especially for lignocellulosic fiber composites, due to their highly hydrophilic nature which impacts the composite performance. This study focuses on bamboo fiber-polypropylene composites manufactured by film stacking using fiber mats obtained through a wet laid process. To individualize fibers, raw bamboo was cooked using an alkaline treatment: the soda process, i.e., using NaOH in order to keep a certain amount of lignin on fiber surface. A maximum surface lignin content of 81.%, measured by XPS analysis, was obtained, from the 1 wt.% NaOH concentration. The corresponding bulk lignin content, measured by Klayson method, is 21.%. The macroscopic properties of bamboo fiber-polypropylene composites were evaluated with regard to material microstructure through a multiscale analysis. The best mechanical properties were obtained for composites manufactured from bamboo fiber prepared using a 1 wt.% NaOH, which corresponds to the highest lignin content (3.5 GPa and 53 MPa for modulus and strength in tensile tests, 3.8 GPa and 64 MPa in bending tests). The good mechanical performance of the composites was attributed to the improved compatibility between the fiber and the matrix, evidenced by multiscale studies.